1. Field of the Invention
The present invention is related to rotatably mounted lamp shades, and particularly to rotatably mounted lamp shades which are structured to be caused to rotate as a result of air convection currents generated by the heat produced by a light bulb that is at least partially covered by the lamp shade.
2. Description of the Prior Art
It is a well known in the art to place a translucent shade over electric light bulbs in order to reduce glare and present a generally pleasing effect to the eye. In this regard, lamp shades have over the years acquired a profusion of various types and shapes which fit essentially every imaginable situation.
One of these situations is that of rotatably mounting the lamp shade in order to create a variating scene or other creative visual effect when the light bulb for which it is mounted is illuminated. Generally, it is acknowledged in the art that to cause a lamp shade to rotate in a most efficient and effective manner, it must be mounted to a stationary lamp structure with a minimum of bearing resistance and, importantly, be capable of being rotated by air convection currents generated by the heat of the adjacent illuminated electric light bulb.
A number of proposals have been presented in the prior art which attempt to achieve adequate rotation speed coupled with reasonable size and weight restrictions. Generally, these proposals fall into two broad categories: singular lamp shades systems and multiple lamp shade systems.
Single lamp shade systems generally consist of a lamp with a rotatably mounted lamp shade. An example of such a system is represented by U.S. Pat. No. 290,489 dated Dec. 18, 1883 to Simpson which discloses a display body encompassing a source of illumination that is heating the air within the display body. The display body has a series of vanes at its uppermost end through which rising heated air circulates. As a result of force applied by the moving air on the vanes, the display body is caused to rotate on a shaft. Examples of similar devices are disclosed in U.S. Pat. Nos. 352,646 dated Nov. 16, 1886 to Gennert; 1,972,687 dated Sept. 4, 1934 to McCoy; and 3,435,201 dated Mar. 25, 1969 to Kemenczky. These devices all suffer from the problem of excessive weight and ineffective production of and control over the air convection currents resulting in sporadic, erratic and slow rotation rates of the lamp shade.
Multiple lamp shade systems generally have a lamp to which is attached both a stationary lamp shade and a coaxially mounted rotatable lamp shade, the interplay between the lamp shades causing a desired visual effect. An example of such a system is represented by U.S. Pat. No. 1,066,493 dated July 8, 1913 to Harrold which discloses a lamp surrounded by a stationary cylindrically shaped exterior lamp shade having a rectangularly shaped aperture on its cylindrical side wall. A cylindrically shaped rotatable lamp shade is coaxially mounted with respect to the stationary lamp shade by a mounting member of the lamp. At the upper end of the cylindrical wall of the rotatable lamp shade is located a series of vanes. Figures are attached to the rotatable lamp shade. When the lamp bulb is illuminated, heat from the bulb causes air to rise through the vanes, making the rotatable lamp shade rotate. Rotation of the rotatable lamp shade causes the figures to periodically pass the rectangular aperture yielding a desired visual effect. Examples of other multiple lamp shade systems are disclosed in U.S. Pat. Nos. 1,178,764 dated Apr. 11, 1916 to Watanabe; 1,865,758 dated July 5, 1932 to Horton; 2,398,974 dated Apr. 23, 1946 to Storm; and dated Sept. 16, 1952. These devices also suffer from the aforementioned problems plaguing single lamp shade systems, namely excessive weight and inability to produce and control air convection currents so that rotary motion of the rotatable lamp shade is sporadic, erratic and slow.
The aforementioned problems could be solved, as exemplified by the patent to Watanabe, by utilizing large and very hot light bulbs within the rotatable lamp shade so as to induce a substantial flow of convecting air through the vanes. However, this has the disadvantage of considerable size, excessive power consumption, and restricted applicability to large lighting environments.
Accordingly, what is needed in the art is a rotatable lamp shade system which derives its rotary movement from convecting air caused by heating of a light bulb including a bulb of small size, wherein the rotatable lamp shade will dependably rotate with a consistent and regular rate of rotation and the rotatable lamp shade has minimal weight because the heat produced by the light bulb is strictly controlled to efficiently heat the adjacent air and the resulting air convention currents are strategically directed to have maximum effect at the vanes.